fix(npm): fix clean script
fix(npm): fix clean script

Currently, npm run clean does nothing. Fix this by updating the syntax
used by rimraf.

adamweeks/spark-js-sdk,adamweeks/spark-js-sdk,adamweeks/spark-js-sdk,aimeex3/spark-js-sdk,mwegman/spark-js-sdk,mwegman/spark-js-sdk,aimeex3/spark-js-sdk,mwegman/spark-js-sdk,aimeex3/spark-js-sdk